<template>
	<div>
		<input ref="excel-upload-input" class="excel-upload-input" type="file" accept=".xlsx, .xls" @change="handleClick">
		<el-button :plain="plain" :disabled="disable" :icon="icon" :loading="loading" :size="size" :type="type" @click="handleUpload">
			{{ showText ? text : '' }}
		</el-button>
	</div>
</template>

<script>
    import XLSX from 'xlsx';

    export default {
        props: {
            size: {
                type: String,
                default: 'small'
            },
            showText: {
                type: Boolean,
                default: true
            },
            type: {
                type: String,
                default: 'primary'
            },
            text: {
                type: String,
                default: '导入'
            },
            icon: {
                type: String,
                default: 'el-icon-download'
            },
            plain: {
                type: Boolean,
                default: false
            },
            disable: {
                type: Boolean,
                default: false
            },
            beforeUpload: Function, // eslint-disable-line
            onSuccess: Function// eslint-disable-line
        },
        data() {
            return {
                loading: false,
                excelData: {
                    header: null,
                    results: null
                }
            };
        },
        methods: {
            generateData({ header, results }) {
                this.excelData.header = header;
                this.excelData.results = results;
                this.onSuccess && this.onSuccess(this.excelData);
            },
            handleDrop(e) {
                e.stopPropagation();
                e.preventDefault();
                if (this.loading) return;
                const files = e.dataTransfer.files;
                if (files.length !== 1) {
                    this.$message.error('Only support uploading one file!');
                    return;
                }
                const rawFile = files[0]; // only use files[0]

                if (!this.isExcel(rawFile)) {
                    this.$message.error('Only supports upload .xlsx, .xls, .csv suffix files');
                    return false;
                }
                this.upload(rawFile);
                e.stopPropagation();
                e.preventDefault();
            },
            handleDragover(e) {
                e.stopPropagation();
                e.preventDefault();
                e.dataTransfer.dropEffect = 'copy';
            },
            handleUpload() {
                this.$refs['excel-upload-input'].click();
            },
            handleClick(e) {
                const files = e.target.files;
                const rawFile = files[0]; // only use files[0]
                if (!rawFile) return;
                this.upload(rawFile);
            },
            upload(rawFile) {
                this.$refs['excel-upload-input'].value = null; // fix can't select the same excel

                if (!this.beforeUpload) {
                    this.readerData(rawFile);
                    return;
                }
                const before = this.beforeUpload(rawFile);
                if (before) {
                    this.readerData(rawFile);
                }
            },
            readerData(rawFile) {
                this.loading = true;
                return new Promise((resolve, reject) => {
                    const reader = new FileReader();
                    reader.onload = e => {
                        const data = e.target.result;
                        const workbook = XLSX.read(data, { type: 'array' });
                        const firstSheetName = workbook.SheetNames[0];
                        const worksheet = workbook.Sheets[firstSheetName];
                        const header = this.getHeaderRow(worksheet);
                        const results = XLSX.utils.sheet_to_json(worksheet);
                        this.generateData({ header, results });
                        this.loading = false;
                        resolve();
                    };
                    reader.readAsArrayBuffer(rawFile);
                });
            },
            getHeaderRow(sheet) {
                const headers = [];
                const range = XLSX.utils.decode_range(sheet['!ref']);
                let C;
                const R = range.s.r;
                /* start in the first row */
                for (C = range.s.c; C <= range.e.c; ++C) { /* walk every column in the range */
                    const cell = sheet[XLSX.utils.encode_cell({ c: C, r: R })];
                    /* find the cell in the first row */
                    let hdr = 'UNKNOWN ' + C; // <-- replace with your desired default
                    if (cell && cell.t) hdr = XLSX.utils.format_cell(cell);
                    headers.push(hdr);
                }
                return headers;
            },
            isExcel(file) {
                return /\.(xlsx|xls|csv)$/.test(file.name);
            }
        }
    };
</script>

<style scoped>
.excel-upload-input{
  display: none;
  z-index: -9999;
}
.drop{
  border: 2px dashed #bbb;
  width: 600px;
  height: 160px;
  line-height: 160px;
  margin: 0 auto;
  font-size: 24px;
  border-radius: 5px;
  text-align: center;
  color: #bbb;
  position: relative;
}
</style>
